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1 Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333
Burnet Ave., Cincinnati, OH 45229-3039.
2 Department of Pediatrics, Cincinnati Children's Hospital Medical Center,
Cincinnati, OH 45229-3039.
3 Department of Otolaryngology, Cincinnati Children's Hospital Medical Center,
Cincinnati, OH 45229-3039.
4 Department of Pulmonology, Cincinnati Children's Hospital Medical Center,
Cincinnati, OH 45229-3039.
Received September 2, 2003;
accepted after revision January 21, 2004.
Address correspondence to L. F. Donnelly
(lane.donnelly{at}chmcc.org).
Abstract
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MATERIALS AND METHODS. Cine MRI studies performed to evaluate persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy were reviewed. MRI was performed under sedation and included cine MR images (fast gradient-echo) obtained in the midline sagittal plane and in the axial plane at the base of the tongue and T1-weighted spin-echo and fast spin-echo inversion recovery images in the axial and sagittal planes. Imaging parameters reviewed included static and dynamic diagnoses made, frequency of recurrence and diameter of tonsillar tissue, and tongue morphology.
RESULTS. Twenty-seven patients were identified (mean age, 9.9 years). Diagnoses included glossoptosis in 17 patients (63%), hypopharyngeal collapse in six (22%), recurrent and enlarged adenoid tonsils in 17 (63%), enlarged lingual tonsils in eight (30%), and macroglossia in 20 (74%). Of the 20 patients with macroglossia, 11 (55%) had absence of the normal median sulcus and 12 (60%) had evidence of fatty infiltration of the tongue musculature.
CONCLUSION. Persistent obstructive sleep apnea in children with Down syndrome who have undergone previous adenoidectomy and tonsillectomy has multiple causes. The most common causes include macroglossia, glossoptosis, recurrent enlargement of the adenoid tonsils, and enlarged lingual tonsils.
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All patients referred for cine MRI were referred clinically. At our institution, clinical indications for cine MRI include persistent obstructive sleep apnea despite previous tonsillectomy, adenoidectomy, or other surgery; obstructive sleep apnea and predisposition to obstruction at multiple sites; and evaluation of any patient with obstructive sleep apnea before complex airway surgery is performed [13]. The patients in this study group met these criteria both by having persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy and by having a predisposition to obstruction at multiple sites related to Down syndrome.
All cine MRI was performed on one of two 1.5-T scanners (Signa, General Electric Medical Systems). The patients were placed in the head–neck vascular coil. Patients were imaged with the cervical spine in the neutral position. The airway was imaged from the most superior aspect of the nasopharynx to the level of the lower cervical trachea. Multiple imaging sequences were performed including axial and sagittal T1-weighted images, axial and sagittal fast spin-echo inversion recovery images, and cine MR images obtained in the midline sagittal location and in the axial plane at the level of the base of the tongue. The sequence used to create the cine MR images was a fast gradient-echo sequence. Technical parameters were TR/TE, 8.2/3.6; flip angle, 80°; and slice thickness, 8 mm. A total of 128 consecutive images were obtained at the same location over an imaging time of approximately 2 min. The sagittal and axial images were then displayed in a cine format creating a real-time "movie" of airway motion. The midline sagittal plane was determined from a combination of 3D localization images and the sagittal and axial T1 data.
All cine MRI studies were performed with the patients sedated. Sedation was performed in one of two methods. Most sedation was performed and monitored in accordance with the radiology department structured sedation program. For such cases a sedation nurse, a pediatric radiologist, and a respiratory therapist equipped with positive-pressure breathing equipment were present during the sedation and MRI. Positive-pressure ventilation equipment is made available in the event that it is required during the examination. Many of these subjects use positive-pressure ventilation devices during sleep at home. In most cases, positive-pressure ventilation is not used during the imaging examination. Patients were sedated with IV pentobarbital (3 mg/kg, with repeated dosing if the patient remained awake for a possible total amount of up to 7 mg/kg). Some patients were sedated by the anesthesiology department using propofol. In no patients, regardless of the type of sedation used, was an artificial airway in place during imaging.
Imaging examinations were evaluated for the following parameters. On fast spin-echo inversion recovery images, tonsillar tissue appears as high in signal in contrast to a low-signal background. The presence of adenoid tonsillar tissue was identified as high-signal soft tissue in the area of the adenoid bed on fast spin-echo inversion recovery images. When the adenoid tonsils were present, their maximal diameter was recorded in the anteroposterior diameter in a manner similar to that reported in the literature [14–16]. Using the midline image, the thickness of the adenoid was measured at the maximal convexity of the adenoid and aligned perpendicular to the anterior clival surface [14–16]. Adenoid tonsils were considered recurrent and enlarged when they measured greater than 12 mm and when intermittent obstruction of the posterior nasopharynx was documented on the sagittal cine MR images. Absence of the palatine tonsils was also documented.
Lingual tonsils were identified as high-signal tissue at the level of the posteroinferior aspect of the tongue in the expected location of the lingual tonsils on fast spin-echo inversion recovery images. The size of the lingual tonsils was measured in the greatest diameter in the axial plane. Lingular tonsils were considered enlarged when both were prominent in size, intermittent obstruction of the hypopharynx was documented at the level of the lingual tonsils, and the lingual tonsils appeared to contribute to the cause of the intermittent airway obstruction. To our knowledge, no reference data have been reported on the expected normal size of the lingual tonsils.
The number of cases with diagnoses of glossoptosis or hypopharyngeal collapse was reviewed. Glossoptosis was defined as predominant posterior motion of the tongue intermittently during the respiratory cycle leading to the intermittent obstruction of the hypopharynx. On sagittal and axial cine images this arrangement is seen as a predominant posterior motion of the tongue without anterior motion of the posterior pharyngeal wall [2, 13]. Hypopharyngeal collapse was defined as intermittent cylindric collapse of the hypopharynx. Axial cine images at the level of mid tongue are helpful in making this determination. On axial cine images, hypopharyngeal collapse is identified by intermittent cylindric motion of the anterior, posterior, and left and right walls of the hypopharynx toward the center point of the hypopharynx. This cylindric motion of all walls of the hypopharynx was a differentiating factor between hypopharyngeal collapse and true glossoptosis [2, 13]. On axial images, glossoptosis is shown as posterior motion of the posterior aspect of the posterior portion of the tongue without significant motion of the posterior or lateral walls of the hypopharynx [2, 13].
The size of the tongue was subjectively identified as either normal or enlarged (macroglossia). Morphology of the tongue was also evaluated for the presence or absence of the medial sulcus on axial images. In addition, the tongue was evaluated for the presence of fatty infiltration, which was shown as increased signal in the muscular substance of the tongue on T1-weighted images. Fatty infiltration was considered to be present when the increased signal in the tongue was in excess of that seen in children without Down syndrome. Most children have minimal or no fatty signal in the musculature of the tongue. Both the size of the tongue and amount of fat in the tongue were subjectively compared with sagittal T1-weighted image sets from children without Down syndrome. These data sets were available to the reviewer when the image data from the patients with Down syndrome were reviewed.
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Diagnoses identified included glossoptosis in 17 patients (63%), hypopharyngeal collapse in six (22%), recurrent and enlarged adenoid tonsils in 17 (63%), enlarged lingual tonsils in eight (30%), and macroglossia in 20 (74%). Multiple patients had more than one diagnosis. Examples of diagnoses are illustrated in Figures 1A, 1B, 1C, 1D, 1E, 2A, 2B, 3A, 3B, 3C, 3D, 4A, 4B, 4C, 4D, 4E, 5A, 5B. When surgically manageable diagnoses (such as recurrent enlarged adenoid tonsils, enlarged lingual tonsils, or glossoptosis) were identified on cine MRI, these conditions were subsequently managed surgically on the basis of the cine MRI results, and in all cases the findings suggested on cine MRI were confirmed.
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Identifiable adenoid tonsillar tissue was present in 23 patients (85%). The mean anteroposterior diameter was 11.4 mm (range, 4.7–25 mm). Again, the adenoids were deemed to be recurrent and enlarged in 17 patients (63%) (Figs. 1A, 1B, 1C, 1D, 1E and 2A, 2B). The palatine tonsils were absent in all patients. The lingual tonsils were present in all 27 patients (100%). The mean maximum diameter of the lingual tonsils was 8.6 mm (range, 4–17 mm). The lingual tonsils were considered enlarged and contributing to airway obstruction in eight patients (30%) (Fig. 3A, 3B, 3C, 3D).
Macroglossia was considered present in 20 patients (74%). Of those 20, 11 (55%) showed absence of the normal median sulcus (Fig. 4A, 4B, 4C, 4D, 4E). Twelve (60%) showed MRI evidence of fatty infiltration in the muscular substance of the tongue (Fig. 4A, 4B, 4C, 4D, 4E).
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At our institution, cine MRI is used as a clinical tool in the evaluation of patients with obstructive sleep apnea in whom previous surgical therapy has failed, who are being considered for complex airway surgery, or who have underlying abnormalities that predispose them to obstruction at multiple levels [13]. Such dynamic imaging studies have been shown to have an effect on management decisions in most cases [13, 16–18]. In our series of patients with Down syndrome, the causes of persistent obstructive sleep apnea were heterogeneous. The most common diagnoses included recurrent and enlarged adenoid tonsils, glossoptosis, hypopharyngeal collapse, enlarged lingual tonsils, and macroglossia. Preliminary data suggest that the degree of obstructive sleep apnea on polysomnography remaining after the second surgical procedure is less when data from cine MRI are used in surgical planning than when they are not. However, these data are preliminary because many subjects in this series are currently active cases and follow-up has been only short-term.
Children with Down syndrome are predisposed to having enlargement of the adenoid and palatine tonsils [1–12]. Several publications have addressed the issue of the frequency in the general population of adenoid regrowth after excision. It is believed that regrowth of the adenoid tonsils after adenoidectomy is uncommon in the general population and uncommonly contributes to recurrent obstructive sleep apnea [19]. In our series, some residual adenoid tonsillar tissue was present in most patients. Recurrent and enlarged adenoid tonsils contributing to intermittent obstruction of the posterior nasopharynx were one of the more often diagnosed causes of persistent obstructive sleep apnea. These findings may suggest that not only do patients with Down syndrome have a predisposition to developing adenoid and palatine tonsil hypertrophy, they may also be predisposed to regrowth of the adenoid tonsils after tonsillectomy.
The relationship between anatomic causes of obstruction, such as enlarged adenoid tonsils, and the presence of obstructive sleep apnea is controversial and has been debated. Some cine MRI data show a correlation between increased dynamic motion of the airway and increased size of the adenoid tonsils in asymptomatic children [16]. These findings support a potential role of enlarged adenoid tonsils in the development of obstructive sleep apnea. Our study does not further investigate the presence or absence of a relationship between enlargement of the adenoid tonsils and obstructive sleep apnea. Our study also does not further evaluate the relationships between anatomic causes and decreased neuromuscular tone to development of obstructive sleep apnea.
Enlargement of the lingual tonsils has been described as a rare cause of significant obstructive sleep apnea in adults [20–24]. It is even more uncommon in children, with only a handful of cases described [21–23]. Of those few cases described in children, at least three are described in patients with Down syndrome. In our series, eight patients were identified in whom the lingual tonsils were enlarged and found on the cine MR images to contribute to obstruction of the hypopharynx. Patients with Down syndrome may be predisposed to hypertrophy not only of the adenoid and palatine tonsils, but also of the lingual tonsils. Compensatory hypertrophy of the lingual tonsils after adenoidectomy and tonsillectomy may occur [24]. Therefore, patients with Down syndrome who have undergone previous tonsillectomy and adenoidectomy may be at particular risk for hypertrophy of the lingual tonsils.
Patients with Down syndrome have macroglossia, and the combination of the enlarged tongue and decreased muscular tone predisposes these patients to glossoptosis that may result in severe obstructive sleep apnea [1–12]. In our series, glossoptosis was one of the most common causes of persistent obstructive sleep apnea, occurring in approximately 63% of patients. Macroglossia was present in approximately 74% of patients. Multiple surgical procedures have been described that aim to either reduce the substance of the posterior aspect of the tongue or reposition the tongue more anteriorly in an attempt to increase the size of the posterior hypopharynx and eliminate intermittent collapse [4, 5, 11, 12, 25, 26]. In reviewing our series of patients with Down syndrome, we noted that in addition to the presence of glossoptosis and macroglossia, a number of additional differences were found in the appearance of the tongue in patients with Down syndrome and macroglossia as compared to the normal MRI appearance of the tongue. In 55% of the patients shown to have macroglossia, the median sulcus, which is normally present in the tongue, was absent. In addition, 60% had increased high signal in the muscular portion of the tongue on T1-weighted images, which is suggestive of fatty infiltration. These findings may suggest that an underlying dysplastic component of macroglossia is present in patients with Down syndrome.
Previous reports have described traditional imaging methods of evaluating the upper airway of children with Down syndrome, including lateral neck radiography, cephalometric measurements, airway fluoroscopy, and nasal pharyngoscopy [5, 10, 17, 26–30]. In addition, the use of MRI in the evaluation of the volumes of soft tissue and the airway in Down syndrome patients without obstructive sleep apnea has been described [31]. Cine MRI is useful in the evaluation of obstructive sleep apnea [15, 16, 18, 32–35]. To our knowledge, our study is the first to use both static anatomic information and dynamic information from cine MRI to evaluate the airway in a series of patients with Down syndrome and obstructive sleep apnea. The use of both static and dynamic information in evaluating the airway may be superior to evaluation by static information alone [15, 16, 18, 32–35].
In conclusion, patients with Down syndrome and persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy may have any of a number of persistent anatomic causes of obstructive sleep apnea. Identification and characterization of these potential causes may be helpful in planning surgical treatment. In addition to having an underlying propensity for hypertrophy of the adenoid and palatine tonsils, patients with Down syndrome may also have a predisposition to recurrence of the adenoid tonsils after adenoidectomy. Hypertrophy of the lingual tonsils, which is an uncommon cause of obstructive sleep apnea in the general population, may also be a common cause of persistent obstructive sleep apnea in this group of patients with Down syndrome. Macroglossia and associated glossoptosis are also common causes of persistent obstructive sleep apnea in these patients. The combination of static and dynamic information obtained on cine MRI may be an optimal way to evaluate these patients.
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